The tasks of the Statistics, Epidemiology, and Data Core (SED) are twofold. One task, to be ongoing through the life of the HIV Center, is to be consultative and integrative. The second task is to establish a data bank, based initially on the already accomplished work of the Center. In setting up this data bank, the Core will take primary responsibility for completion of the remaining analytic tasks of HIV Center I, and particularly, although not only, for those concerning the Follow-up Project.